| Details: |
The importance of relativistic effects in chemistry is illustrated by the fact that without relativity gold would
have the same color as silver [1–3], mercury would not be liquid at room temperature [4, 5] and your car would not
start [6]. Two kinds of relativistic effects are commonly distinguished, namely scalar-relativistic effects and spin-orbit
interaction.
In my lecture I consider chemical bonding in f-element compounds. Two specific cases will be adressed:
1. A central question of f-element chemistry is whether the f orbitals participate in bonding. Ligand X-ray absorption
spectroscopy has been used to probe covalency in transition metal complexes [7]. More recently this
approach has been extended to f-element compounds [8]. I will take a critical look at what we actually learn
from this approach.
2. In a seminal paper [9], Gagliardi and Roos presented the first computational evidence that U2 is a stable molecule,
suggesting one of the most complex electronic structures hitherto known for any two atoms in a molecule, with
a quintuple bond. Their analysis, however, did not take into account the possible effect of spin-orbit interaction.
In a recent study [10]we show that the variational inclusion of spin-orbit interaction leads to not only a different
electronic ground state, but also a lower bond multiplicity compared to previous studies.
References
[1] N. Egede Christensen and B. O. Seraphin. Relativistic Band Calculation and the Optical Properties of Gold. Phys. Rev. B, 4:3321–
3344, Nov 1971.
[2] P. Romaniello and P. L. de Boeij. The role of relativity in the optical response of gold within the time-dependent current-densityfunctional
theory. The Journal of Chemical Physics, 122(16):164303, 2005.
[3] Kathrin Glantschnig and Claudia Ambrosch-Draxl. Relativistic effects on the linear optical properties of Au, Pt, Pb and W. New
Journal of Physics, 12(10):103048, 2010.
[4] Florent Calvo, Elke Pahl, Michael Wormit, and Peter Schwerdtfeger. Evidence for Low-Temperature Melting of Mercury owing to
Relativity. Angewandte Chemie International Edition, 52(29):7583–7585, 2013.
[5] Krista G. Steenbergen, Elke Pahl, and Peter Schwerdtfeger. Accurate, Large-Scale Density Functional Melting of Hg: Relativistic
Effects Decrease Melting Temperature by 160 K. The Journal of Physical Chemistry Letters, 8(7):1407–1412, 2017.
[6] Rajeev Ahuja, Andreas Blomqvist, Peter Larsson, Pekka Pyykk¨o, and Patryk Zaleski-Ejgierd. Relativity and the Lead-Acid Battery.
Phys. Rev. Lett., 106:018301, Jan 2011.
[7] Edward I. Solomon, Britt Hedman, Keith O. Hodgson, Abhishek Dey, and Robert K. Szilagyi. Ligand K-edge X-ray absorption
spectroscopy: covalency of ligand-metal bonds. Coord. Chem. Rev., 249(1-2):97 – 129, 2005.
[8] Michael L. Neidig, David L. Clark, and Richard L. Martin. Covalency in f-element complexes. Coord. Chem. Rev., 257(2):394 – 406,
2013.
[9] L. Gagliardi and B. Roos. Quantum chemical calculations show that the uranium molecule u2 has a quintuple bond. Nature, 433:848,
2005.
[10] Hans Jørgen Aa. Jensen Stefan Knecht and Trond Saue. Relativistic quantum chemical calculations show that the uranium molecule
U2 has a quadruple bond. Nature Chemistry, 2018. |